1. Field of the Invention
The present invention relates to systems which simultaneously display graphic, character, and other images on a matrix screen and then rotate the image. It relates specifically to a road map labeled with alphanumeric characters.
2 Description of the Prior Art
A conventional display system of the type which is, for example, mounted in front of the driver'seat of an automotive vehicle for displaying a road map on a screen includes a single memory for storing all graphic pattern data. This memory has a storage capacity corresponding to the number of picture elements on the display screen such that the graphic data, character data, and other data (such as size and position data for the characters constituting each word indicating, e.g., a place-name) are stored integrally. The display system also includes a signal generator for generating and outputting a rotation angle signal to rotate the graphic image on the screen, such as from a vehicle traveling directional detector of the type disclosed in U.S. Pat. No. 2,464,057, which outputs a voltage signal which varies according to changes in the direction in which the vehicle travels, and a display control circuit which controls the data stored in the graphic memory according to the rotation angle signal from the signal generator.
Such a conventional display system as described above, however, has the problem that the characters displayed with the map are rotated along with the map. Thus, it takes time for a driver to recognize the alphanumerals and marks superimposed on the map pattern, reversed or inclined as they are with respect to upright on the screen, after the image on the screen is rotated through an angle according to the change in traveling direction of the automotive vehicle.